Adult cynomolgus monkeys (Macaca fascicularis) will be given a semipurified diet containing 34 mg of cholesterol/100 kcal for 3 months, and will also receive cholesterol binding alfalfa saponins (CBAS). The effect of CBAS on plasma cholesterol and on sterol balance will be determined. The mechanism of action of CBAS will be studied, and possible toxicity of CBAS will be determined. If CBAS consistently show hypocholesterolemic effect, an experiment to determine whether CBAS arrest the progression of coronary atherosclerosis will then be performed. Monkeys will be given a semipurified diet containing 120 mg of cholesterol/100 kcal for 6 months. They will be randomly assigned to 3 groups of 20 animals each: (A) baseline control group; (3) slow progression group; (C) test group. Group A will be killed at month 6; groups B and C at month 24. Groups B and C will receive a semipurified diet containing 34 mg/100 kcal from month 6 through 24, and animals from group C will receive in addition CBAS. Plasma cholesterol will be measured bi-monthly and the extent of coronary atherosclerosis will be determined. The aorta, and carotid, mesenteric, renal, and femoral arteries will also be studied.